WebAudio Worklets not working in Firefox

Please include the following in your bug report:

**Version of emscripten/emsdk:**
Anything from `4.0.8` to `4.0.13`

Repo for reproducing is right [here](https://github.com/Andonvr/webaudio-reproducible-bug) <--

This works in Chrome and Safari, but is broken in Firefox.

I followed the guide on Wasm Audio Worklets from [here](https://emscripten.org/docs/api_reference/wasm_audio_worklets.html), and adjusted it slightly.
Basically, I added a class to hold a gain value, which I expose using Embind. When creating the Audio Worklet, I pass an instance of it. Later, I change the value of this, and the gain adjusts.

I compile, using CMake, and run using the most simple Vite project.

All of this works perfectly in Chrome.
But in Firefox, when creating the Wasm Audio Worklet (and not anywhere before that), it throws the error `RuntimeError: index out of bounds`.

With the compiler flag `WEBAUDIO_DEBUG`, it even prints "Registered new WebAudio object [object AudioWorkletNode] with ID 2" before failing.